Rotative drives have been installed to serve as servo or control means in many applications, especially in machine tools and motor vehicles. In the case of electrically activated rotative drives, as a rule, blocking or brake apparatuses are present for prevention of under or over runs. Besides some shape fit mechanisms, the blocking or braking apparatuses can often be found as electro-magnetic shifting frictional clutches and brakes.
In accordance with the character of a major interruption, one must make a distinction between power loss during operation wherein engagement of the brake can only be attained by residual voltage and, contrarily, a power loss while equipment is idle wherein disengagement of the brake can only be executed by possible backup voltage.
In a case of backup voltage braking, if this voltage should fail, then the brake engages itself. Some known designs have the capability of overcoming a field of a parallel placed permanent magnet, via an electrically energized coil, whereby the brake is held in its disengaged position. On the other hand, in a case of total voltage failure, only the magnetic field of a permanent magnet can exist whereby a brake will engage. This type of assembly is adapted to applications, which require an absolute engagement of a brake when voltage is lost so that, for example, a positioning or a control operation can be brought to a stop. For example, one application to the furnish acting stabilizers for roll control of motor vehicles wherein the stabilizer halves, when brakes are disengaged, are such that the halves positionally oppose one another. Contrarily, if brakes are disengaged then the stabilizer halves become firmly coupled together. In the case of an electric power failure, a rigid stabilizer is required so that the brake is immediately blocked.
If power failure should occur in the use of rotative bodies which turn toward each other, then their relative positioning is immediately fixed. In the case of the above mentioned application, where an activated stabilizer is involved, it is possible for a drive-dynamic maneuver in the interface area to be carried out at the instant of engagement. Consequently, in a case of defection, during a turn into a fast lane, a stabilizer with rotated halves is blocked. Upon a renewed change back to a travel lane, then the stabilizer is so stressed that its action is largely suspended or can only be put into action by a very large chassis rolling. Thereby, driving stability is lost up to the point of danger of upset.
DE 693 02 712 T2 teaches that a vehicle with stabilizers on the front and rear axles, the stabilizing halves can be pivoted toward one another by a servo motor. In this arrangement, no braking assembly is provided between the stabilizer halves.
With this background, the purpose of this invention is to achieve improvements with regard to the state of the technology and to create a backup current apparatus, which can assure increased safety even in the case of an external defect in dynamically critical situations. This relates especially to applications involving stabilizers on motor vehicles.